GEN CHEM DESTROYER QUESTION

[csulapredental]

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#92
Consider the following reactino:

4H+ (aq) + O2 (g) + 4 e- <-- --> 2H2O (l)
If sodium hydroxide is added, and assuming O2 (g) is at 1 atm and [H+] = 1.0 M, which statement is true?

a) The E value would not change since base is not a part of this system
b) E value would increaes
c) The reaction quotient would take H2O (l) into account
d) two of these are true
e) none ofthese are true


My [h+] is going down.. so doesn't that mean B is true
in back it says [A] increases E would decrease
and if B increases E would increase

 

[Don Kim]

E = Eo - 0.0592/n(logQ)
So logQ = 1/([H+][O2])
Try doing this to help make sense of it: Let's say Q of logQ was 1/100. That gives a logQ value of -2. Now, the denominator decreases to 10 to give Q = 1/10. Now logQ is -1. did logQ increase of decrease? Increased (-2 => -1)
But you are looking for E, not logQ, so now plug it in to the equation.
Eo - 0.0592/n(-2) vs. Eo - 0.0592/n(-1) --> Eo + 2(0.0592/n) > Eo + 0.0592/n-> The logQ changed from -2 to -1 but the original value is greater. So the E value decreased, not increased.